Epidemiologic studies of occupational groups are valuable since workers often have heavy and prolonged exposures to carcinogens also found in the general environment. Completed during the past year were studies of 1) professional artists revealing an excess of leukemia and cancers of the bladder, kidney, brain, colon, prostate, and breast; 2) lung cancer among foundry workers showing excessive risks among younger workers employed in iron foundries; 3) embalmers exposed to formaldehyde were slightly increased mortality from cancers of the skin, kidney, and brain were noted; 4) workers in the petroleum industry which uncovered excess mortality from leukemia, multiple myeloma, lymphoma, and brain cancer; 5) a small number of chemical workers exposed to benzene who had a significant excess of leukemia; and 6) veterinarians whose mortality from leukemia was elevated particularly among those practicing during the late l950's and early l960's when radiologic procedures were less carefully controlled. Other investigations under way include proportionate mortality studies of plumbers, foresters, and millers; cohort mortality studies of formaldehyde workers, dry cleaners, furniture makers, shipyard workers, aircraft mechanics, potters, and chemists; and case-control studies of leukemia, lymphoma, soft-tissue sarcoma, and cancers of the brain and colon.